(1) Field of the Invention
The present invention relates to a steered pair of radial tires for use in high speed vehicles. For example, such a steered pair of radial tires produce great cornering forces particularly at large cornering angles, when they are applied to low aspect ratio pneumatic radial tires.
(2) Related Art Statement
A tread pattern shown in FIG. 4 is available by way of example for known high speed vehicle radial tires having an asymmetrical pattern and a directional property.
FIG. 4 shows the tread pattern as viewed from the front side of a tire which is fitted to a left front wheel of a vehicle as a steering wheel. A right front wheel tire has a tread pattern having an axially symmetrical relationship to that in FIG. 4.
In FIG. 4, an arrow A shows a rotational direction of the tire, and reference numerals 1 and 2 show a tread and a treading surface, respectively.
In the illustrated tread pattern, annular land portions are formed by providing four circumferential main grooves 3 through 6 extending linearly in the circumferential direction of the tire in the treading surface 2 of the tread. As viewed in the front view of the tire, a plurality of bent main grooves 7 extend over the entire width of the tread in the almost L-letter shaped form, while the main grooves 7 are bent at the circumferential main groove 5. Thereby, plural rows 8 through 12 of blocks are formed in the land portions, respectively. By employing such a tread pattern, the wear resistance of the tire is improved, and noise of the pattern is reduced.
Considering gripping performance on dry roads in above conventional tire, sufficiently great cornering forces can be produced in a range of small cornering angles, in other words, at small slip angles, as shown in FIG. 5 by a solid line. However, the cornering forces unfavorably rapidly drop in a range of great slip angles. As clearly shown in a foot print of FIG. 6, water drain grooves having an almost V-letter shape are backwardly formed in an advancing or forwardly rotational direction B of the tire. Consequently, there is a possibility that the bent transverse main grooves 7 themselves cannot completely drain all water entering the transverse main grooves 7 from the front side in the advancing or forwardly rotating direction of the tire irrespective of the magnitude of the cornering angles. Therefore, such a tire has a problem in that a hydroplaning phenomenon is likely to occur.